The present invention relates generally to an image editing apparatus for editing digital video signals. This image editing apparatus is suitably for use in editing systems of broadcast stations (for example, broadcast stations of broadcasting industries, office broadcast stations, and school broadcast stations) providing services such as broadcast communication for general public and simultaneous transmissive communication for specified members or in editing systems such as post-production.
Post-production herein denotes producing such titles (or video content) completed in terms of audio and video as broadcast programs, TV commercials, and video packages by use of sophisticated editing techniques and composing techniques on the basis of audio and video materials recorded on video tape, disk, film, and so on. Especially, post-production denotes the operation for carrying out these activities.
Generally, it is indispensable for broadcast stations and post-production companies to carry out jobs of cutting out necessary portions of material and connecting the cuts into desired video content. Conventionally, editing machines used for such editing jobs are so-called linear editing machines based on magnetic tape. However, because these tape-based machines are not capable of doing delicate editing jobs on a frame basis and take a long time in doing editing jobs, they are recently being replaced by digital nonlinear editing machines based on storage devices such as hard disk.
The nonlinear editing machine is capable of randomly accessing material in a frame basis. Therefore, the nonlinear editing machine is advantageous in doing delicate editing jobs and avoiding the deterioration of video signals by storing them in a digital format.
The editing jobs by nonlinear editing machines are substantially the same as those by linear editing machines. Namely, “rough editing” (necessary portions of material are roughly cut out and recorded) is executed first; then “fine editing” (precise cut-out is done on a frame basis) is performed on the results of rough editing.
A definite difference from the linear editing machine lies in that the nonlinear editing machine generates information about the results of the above-mentioned rough and fine editing jobs (this information is hereafter referred to as editing result information) and holds the generated information separately from the material to be edited. The editing result information includes the information for use in identifying materials to be edited and the information for use in identifying cut-out start and end points. On the basis of this editing result information, the nonlinear editing machine reproduces the material to be edited. In other words, while the linear editing machine performs editing directly on the material to be roughly edited itself, the nonlinear editing machine performs indirect editing by generating the above-mentioned editing result information without manipulating the rough edit material.
The editing result information is described in a format called an EDL (Edit Decision List). One EDL includes fine edit information (for example, place at which the material was taped, material name, edit point information, and so on) about all materials constituting one piece of video content. On the basis of this EDL, the nonlinear editing machine retrieves a predetermined portion (a portion specified by the edit point information, namely a fine edit portion) of each material from a storage device, connects the retrieved portions according to reproduction sequence information, and reproducibly outputs a series of resultant video content.
In terms of the storage capacity of these nonlinear editing machines for recording materials, however, the nonlinear editing machine is disadvantageous as compared with the linear editing machine using the magnetic tapes. Although the storage capacities of hard disk and other storage media have been remarkably increasing these days, the storage size of each device is several gigabytes at most. To compensate for this shortcoming, a nonlinear editing machine realizing a mass storage size has recently come into practical use by taking advantage storage device arraying technologies represented by RAID (Redundant Array of Inexpensive Disk).
Broadcasting stations and post-production companies are various in business size and irregular in the amount of materials to be handled. That is, the material storage size of the nonlinear editing machine differs from one editing system to another in general. Therefore, in order to enhance the flexibility of the system configuration, the storage size required for each editing system is satisfied by combining basic units of a storage system such as a hard disk system having a predetermined storage size. If the basic unit is called a volume for convenience, a small-scale editing system is equipped with the relatively small number of volumes while a large-scale editing system with the relatively large number of volumes, thereby flexibly coping with editing systems of various scales.
However, with a nonlinear editing machine having two or more volumes, the pieces of information of different volumes (in which recordings are stored) exist together in one EDL. This presents a problem of complicating the control of material reproduction to be executed according to the EDL.
If material is reproduced according to the EDL that includes plural pieces of information about storage devices of recordings, the nonlinear editing machine must sequentially retrieve the information about storage devices of recordings from one EDL and, on the basis of the retrieved information, execute control operations such as port switching in a properly timed relation. Originally, however, the EDL has been applied to nonlinear editing machines having a single volume. Therefore, the above-mentioned control such as port switching is an additional task, which consequently increases the control burden of the nonlinear editing machine.